상세정보
학술지
Ultrafast Photocarrier Dynamics Related to Defect States of Si1_xGex Nanowires Measured by Optical Pump-THz Probe Spectroscopy
- 저자
- 배정민, 이우정, 정성훈, 마진원, 정광식, 오승훈, 김성신, 서동찬, 송우빈, 김선정, 박재헌, 조만호
- 발행일
- 201706
- 출처
- Nanoscale, v.9 no.23, pp.8015-8023
- ISSN
- 2040-3364
- 출판사
- Royal Society of Chemistry (RSC)
- 협약과제
- 16PB2200, 초경량 유연 CIGS 박막 모듈 공정장비 상용화 기술개발, 정용덕
- 초록
- Slightly tapered Si1-xGex nanowires (NWs) (x = 0.29-0.84) were synthesized via a vapor-liquid-solid procedure using Au as a catalyst. We measured the optically excited carrier dynamics of Si1-xGex NWs as a function of Ge content using optical pump-THz probe spectroscopy. The measured -?봗/T0 signals of Si1-xGex NWs were converted into conductivity in the THz region. We developed a fitting formula to apply to indirect semiconductors such as Si1-xGex, which explains the temporal population of photo-excited carriers in the band structure and the relationship between the trapping time and the defect states on an ultrafast time scale. From the fitting results, we extracted intra- and inter-valley transition times and trapping times of electrons and holes of Si1-xGex NWs as a function of Ge content. On the basis of theoretical reports, we suggest a physical model to interpret the trapping times related to the species of interface defect states located at the oxide/NW: substoichiometric oxide states of Si(Ge)0+,1+,2+, but not Si(Ge)3+, could function as defect states capturing photo-excited electrons or holes and could determine the different trapping times of electrons and holes depending on negatively or neutrally charged states.
- KSP 제안 키워드
- Charged states, Fitting formula, Ge content, Indirect semiconductors, Interface defect states, Photo-excited, Physical model, Substoichiometric oxide, Time Scale, Vapor-liquid-solid, band structure